System for determining characteristics of substrates employing fluid geometries

ABSTRACT

The present invention provides a technique for determining characteristics of substrates, such as the presence of contaminants, shape, as well as the spatial relationships between spaced-apart substrates. The spatial relationships include distance and angular orientation, between first and second spaced apart substrates. The technique includes forming a volume of fluid on the second substrate, with the volume of fluid having an area associated therewith. The volume of fluid is compressed between the first and second substrates to effectuate a change in properties of the area, defining changed properties. The changed properties are sensed, and the characteristics of the first and second substrates are determined as a function of the changed properties.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional application of U.S. patentapplication Ser. No. 10/318,365 entitled METHOD FOR DETERMININGCHARACTERISTICS OF SUBSTRATES EMPLOYING FLUID GEOMETRIES, filed Dec. 12,2002, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

The present invention relates generally to lithography systems. Moreparticularly, the present invention is directed to determining spatialrelationships between an imprinting mold and a substrate upon which apattern will be formed using the imprinting mold.

Imprint lithography has shown promising results in fabrication ofpatterns having feature sizes smaller than 50 nm. As a result, manyprior art imprint lithography techniques have been advocated. U.S. Pat.No. 6,334,960 to Willson et al. discloses an exemplary lithographyimprint technique that includes providing a substrate having a transferlayer. The transfer layer is covered with a polymerizable fluidcomposition. A mold makes mechanical contact with the polymerizablefluid. The mold includes a relief structure, and the polymerizable fluidcomposition fills the relief structure. The polymerizable fluidcomposition is then subjected to conditions to solidify and polymerizethe same, forming a solidified polymeric material on the transfer layerthat contains a relief structure complimentary to that of the mold. Themold is then separated from the solid polymeric material such that areplica of the relief structure in the mold is formed in the solidifiedpolymeric material. The transfer layer and the solidified polymericmaterial are subjected to an environment to selectively etch thetransfer layer relative to the solidified polymeric material to form arelief image in the transfer layer.

U.S. Pat. No. 5,772,905 to Chou discloses a lithographic method andapparatus for creating patterns in a thin film coated on a substrate inwhich a mold, having at least one protruding feature, is pressed into athin film carried on a substrate. The protruding feature in the moldcreates a recess in the thin film. The mold is removed from the thinfilm. The thin film then is processed such that the thin film in therecess is removed exposing the underlying substrate. Thus, patterns inthe mold are replaced in the thin film, completing the lithographyprocess. The patterns in the thin film will be, in subsequent processes,reproduced in the substrate or in another material which is added ontothe substrate.

Yet another imprint lithography technique is disclosed by Chou et al. inUltrafast and Direct Imprint of Nanostructures in Silicon, Nature, Col.417, pp. 835-837, June 2002, which is referred to as a laser assisteddirect imprinting (LADI) process. In this process a region of asubstrate is made flowable, e.g., liquefied, by heating the region withthe laser. After the region has reached a desired viscosity, a mold,having a pattern thereon, is placed in contact with the region. Theflowable region conforms to the profile of the pattern and is thencooled, solidifying the pattern into the substrate.

An important consideration when forming patterns in this manner is tomaintain control of the distance and orientation between the substrateand the mold that contains the pattern to be recorded on the substrate.Otherwise, undesired film and pattern anomalies may occur.

There is a need, therefore, for accurately determining spatialrelationships between a mold and a substrate upon which the mold willform a pattern using imprinting lithographic processes.

SUMMARY OF THE INVENTION

The present invention provides a system for determining characteristicsof a first substrate, lying in a first plane, and a second substrate,lying in a second plane with a volume of fluid disposed therebetween.The system includes a displacement mechanism to cause relative movementbetween the volume and one of the first and second substrates toeffectuate a change in properties of an area of the fluid, definingchanged properties. A detector system senses the changed properties andproduces data in response thereto. A processing system receives the dataand produces information corresponding to the characteristics. These andother embodiments are discussed more fully below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified plan view of a lithographic system incorporatinga detection system in accordance with one embodiment of the presentinvention;

FIG. 2 is a partial simplified elevation view of a lithographic systemshown in FIG. 1;

FIG. 3 is a simplified representation of material from which animprinting layer, shown in FIG. 2, is comprised before being polymerizedand cross-linked;

FIG. 4 is a simplified representation of cross-linked polymer materialinto which the material, shown in FIG. 3, is transformed after beingsubjected to radiation;

FIG. 5 is a simplified elevation view of a mold spaced-apart from animprinting layer, shown in FIG. 1, after patterning of the imprintinglayer;

FIG. 6 is a simplified elevation view of an additional imprinting layerpositioned atop of the substrate, shown in FIG. 5, after the pattern inthe first imprinting layer is transferred therein;

FIG. 7 is a top-down view of a region of a wafer, shown in FIG. 1, thatis sensed by a detection system shown therein in accordance with oneembodiment of the present invention;

FIG. 8 is a cross-section of the resulting shape of an imprinting layershown in FIG. 1, being formed with the mold and the wafer not being inparallel orientation with respect to one another;

FIG. 9 is a top-down view of a region of a wafer, shown in FIG. 1, thatis sensed by a detection system shown therein in accordance with analternate embodiment of the present invention;

FIG. 10 is a top-down view of a region of a wafer, shown in FIG. 1, thatis sensed by a detection system shown therein in accordance with anotheralternate embodiment of the present invention;

FIG. 11 is a simplified plan view of a lithographic system incorporatinga detection system in accordance with a second embodiment of the presentinvention; and

FIG. 12 is a simplified plan view of a lithographic system incorporatinga detection system in accordance with a third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a lithographic system 10 in which a detection system inaccordance with one embodiment of the present invention is included.System 10 includes an imprint head 12 and a stage 14, disposed oppositeto imprint head 12. A radiation source 16 is coupled to system 10 toimpinge actinic radiation upon motion stage 14. To that end, imprinthead 12 includes a throughway 18 and a mirror 20 couples actinicradiation from radiation source 16, into throughway 18, to impinge upona region 22 of stage 14. Disposed opposite to region 22 is a detectionsystem that includes a CCD sensor 23 and wave shaping optics 24. CCDsensor 23 is positioned to sense images from region 22. Detection systemis configured with wave shaping optics 24 positioned between CCD sensor23 and mirror 20. A processor 25 is in data communication with CCDsensor 23, imprint head 12, stage 14 and radiation source 16.

Referring to both FIGS. 1 and 2, connected to imprint head 12 is a firstsubstrate 26 having a mold 28 thereon. First substrate 26 may be held toimprint head 12 using any known technique. In the present example firstsubstrate 26 is retained by imprint head 12 by use of a vacuum chuck(not shown) that is connected to imprint head 12 and applies a vacuum tofirst substrate 26. An exemplary chucking system that may be included isdisclosed in U.S. patent application Ser. No. 10/293,224 entitled “AChucking System for Modulating Shapes of Substrates”, which isincorporated by reference herein. Mold 28 may be planar or include afeature thereon. In the present example, mold 28 includes a plurality offeatures defined by a plurality of spaced-apart recessions 28 a andprotrusions 28 b. The plurality of features defines an original patternthat is to be transferred into a second substrate, such as wafer 30,coupled to stage 14. To that end, imprint head 12 is adapted to movealong the Z axis and vary a distance “d” between mold 28 and wafer 30.Stage 14 is adapted to move wafer 30 along the X and Y axes, with theunderstanding that the Y axis is into the sheet upon which FIG. 1 isshown. With this configuration, the features on mold 28 may be imprintedinto a flowable region of wafer 30, discussed more fully below.Radiation source 16 is located so that mold 28 is positioned betweenradiation source 16 and wafer 30. As a result, mold 28 is fabricatedfrom material that allows it to be substantially transparent to theradiation produced by radiation source 16, such as fused silica orquartz glass.

Referring to both FIGS. 2 and 3, a flowable region, such as animprinting layer 34, is disposed on a portion of surface 32 thatpresents a substantially planar profile. Flowable region may be formedusing any known technique such as a hot embossing process disclosed inU.S. Pat. No. 5,772,905, which is incorporated by reference in itsentirety herein, or a laser assisted direct imprinting (LADI) process ofthe type described by Chou et al. in Ultrafast and Direct Imprint ofNanostructures in Silicon, Nature, Col. 417, pp. 835-837, June 2002. Inthe present embodiment, however, flowable region consists of imprintinglayer 34 being deposited as a plurality of spaced-apart discrete beads36 of material 36 a on wafer 30, discussed more fully below. Imprintinglayer 34 is formed from a material 36 a that may be selectivelypolymerized and cross-linked to record the original pattern therein,defining a recorded pattern. Material 36 a is shown in FIG. 4 as beingcross-linked at points 36 b, forming cross-linked polymer material 36 c.

Referring to FIGS. 2, 3 and 5, the pattern recorded in imprinting layer34 is produced, in part, by mechanical contact with mold 28. To thatend, imprint head 12 reduces the distance “d” to allow imprinting layer34 to come into mechanical contact with mold 28, spreading beads 36 soas to form imprinting layer 34 with a contiguous formation of material36 a over surface 32. Were mold 28 provided with a planar surface,distance “d” would be reduced to provide imprinting layer 34 with asubstantially planar surface. In the present example, distance “d” isreduced to allow sub-portions 34 a of imprinting layer 34 to ingressinto and fill recessions 28 a.

To facilitate filling of recessions 28 a, material 36 a is provided withthe requisite properties to completely fill recessions 28 a whilecovering surface 32 with a contiguous formation of material 36 a. In thepresent example, sub-portions 34 b of imprinting layer 34 insuperimposition with protrusions 28 b remain after the desired, usuallyminimum distance “d”, has been reached, leaving sub-portions 34 a with athickness t₁, and sub-portions 34 b with a thickness, t₂. Thicknesses“t₁” and “t₂” may be any thickness desired, dependent upon theapplication. Typically, t₁ is selected so as to be no greater than twicethe width u of sub-portions 34 a, i.e., t₁<2u, shown more clearly inFIG. 5.

Referring to FIGS. 2, 3 and 4, after a desired distance “d” has beenreached, radiation source 16, shown in FIG. 1, produces actinicradiation that polymerizes and cross-links material 36 a, formingcross-linked polymer material 36 c. As a result, the composition ofimprinting layer 34, transforms from material 36 a to material 36 c,which is a solid. Specifically, material 36 c is solidified to provideside 34 c of imprinting layer 34 with a shape conforming to a shape of asurface 28 c of mold 28, shown more clearly in FIG. 5. After imprintinglayer 34 is transformed to consist of material 36 c, shown in FIG. 4,imprint head 12, shown in FIG. 2, is moved to increase distance “d” sothat mold 28 and imprinting layer 34 are spaced-apart.

Referring to FIG. 5, additional processing may be employed to completethe patterning of wafer 30. For example, wafer 30 and imprinting layer34 may be etched to transfer the pattern of imprinting layer 34 intowafer 30, providing a patterned surface 32 a, shown in FIG. 6. Tofacilitate etching, the material from which imprinting layer 34 isformed may be varied to define a relative etch rate with respect towafer 30, as desired. The relative etch rate of imprinting layer 34 towafer 30 may be in a range of about 1.5:1 to about 100:1.

Alternatively, or in addition to, imprinting layer 34 may be providedwith an etch differential with respect to photo-resist material (notshown) selectively disposed thereon. The photo-resist material (notshown) may be provided to further pattern imprinting layer 34, usingknown techniques. Any etch process may be employed, dependent upon theetch rate desired and the underlying constituents that form wafer 30 andimprinting layer 34. Exemplary etch processes may include plasmaetching, reactive ion etching, chemical wet etching and the like.

Referring to both FIGS. 1 and 2, an exemplary radiation source 16 mayproduce ultraviolet radiation. Other radiation sources may be employed,such as thermal, electromagnetic and the like. The selection ofradiation employed to initiate the polymerization of the material inimprinting layer 34 is known to one skilled in the art and typicallydepends on the specific application which is desired. Furthermore, theplurality of features on mold 28 are shown as recessions 28 a extendingalong a direction parallel to protrusions 28 b that provide across-section of mold 28 with a shape of a battlement. However,recessions 28 a and protrusions 28 b may correspond to virtually anyfeature required to create an integrated circuit and may be as small asa few tenths of nanometers. As a result, it may be desired tomanufacture components of system 10 from materials that are thermallystable, e.g., have a thermal expansion coefficient of less than about 10ppm/degree Centigrade at about room temperature (e.g. 25 degreesCentigrade). In some embodiments, the material of construction may havea thermal expansion coefficient of less than about 10 ppm/degreeCentigrade, or less than 1 ppm/degree Centigrade.

Referring to FIGS. 1, 2 and 7, an important consideration tosuccessfully practice imprint lithography techniques is accuratelydetermining distance “d”. To that end, the detection system of thepresent invention is configured to take advantage of the change in thegeometry of beads 36 as the distance “d” is reduced. Assuming beads 36behave as a non-compressible fluid with a volume “v”, distance “d” maybe defined as follows:d= ^(v)/_(A)  (1)where A is a liquid filled area measured by CCD sensor 23. To that end,the combination of CCD sensor 23 and wave shaping optics 24 allows thedetection system to sense one or more beads 36 in region 22. With firstsubstrate 26 spaced-apart from wafer 30, the volume of one or more beads36 provides each bead 36 with an area 40 associated therewith. Asdistance “d” is reduced and substrate 26 comes into mechanical contactwith beads 36, compression occurs. This compression effectuates a changein properties of the area 40 of beads 36, referred to as changedproperties. These changes relate to the geometries of one or more beads36, such as the shape, size or symmetry of the area 40. In the presentexample the changed properties are shown as 42 and concern the size ofthe area 40. Specifically, the compression results in the area 40 ofbeads 36 increasing.

The change in area 40 is sensed by CCD sensor 23, which produces datacorresponding to the same. Processor 25 receives the data correspondingto the change in the area 40 and calculates, using equation 1, thedistance “d”. Assuming CCD sensor 23 consists of a N×M array of pixels,distance “d” is ascertained by processor 25 through the followingequation:d= ^(V)/_(t) _(p) ^((P) ^(a) ⁾  (2)where t_(p) is the total number of pixels in the N×M array and P_(a) isthe area of each pixel.

With volume of beads 36 being fixed, the resolution of CCD sensor 23that is desired to accurately measure the area A may be defined asfollows:ΔA=(^(A)/_(d))Δd  (3)Assuming that the total volume, v, of one of beads 36 sensed by CCDsensor 23 is 200 nl, i.e., 0.1 mm³ and d=200 nm, then liquid filled area“A” is 1000 mm². From equation (2) it may be determined that the desiredresolution of CCD sensor 23 is 5 mm².

It should be noted that processor 25 may be employed in a feedback loopoperation. In this manner, distance “d” may be calculated multiple timesuntil it is determined that the desired distance “d” has been reached.Such calculations may be performed dynamically in real time, orsequentially, with the distance “d” being determined as incrementalmovements of imprint head 12 along the Z axis occur. Alternatively, orin addition thereto, processor 25 may be in data communication with amemory 27 that includes computer-readable information in the form of alook-up table 29. The information in look-up table 29 may includegeometries, shown as 31 a, 31 b and 31 c as related to differingdistances, shown as d_(a), d_(b) and d_(c). In this manner, informationconcerning the geometry of one or more beads 36 may be obtained by CCDsensor 23 and received by processor 25. The information is thenprocessed to relate the same to the geometry in look-up table 29 thatmost closely matches the geometry of the one or more beads 36 sensed byCCD sensor 23. Once a match is made, processor 25 determines a magnitudeof distance “d” present in look-up table 29 that is associated with thematching geometry.

Additional information concerning characteristics of first substrate 26and wafer 30 other than the distance “d” therebetween may be obtained byanalyzing the fluid geometry of one or more beads 36. For example, byanalyzing the symmetry of beads 36 an angular orientation between firstsubstrate 26 and wafer 30 may be determined. Assume first substrate 26lies in a first plane P₁ and wafer 30 lies in a second plane P₂.Assuming area 40 is radially symmetric, any loss of radial symmetry inarea 40 may be employed to determine that first plane P₁ and secondplane P₂ do not extend parallel to one another. Additionally, dataconcerning the shape of area 40, in this case the lack of radialsymmetry, may be employed to determine the angle θ formed between firstand second planes P₁ and P₂ and, therefore, between first substrate 26and wafer 30, shown in FIG. 8. As a result, undesired thicknesses inimprinting layer 34 may be ascertained and, therefore, avoided. Otherinformation may be obtained, as well, such as the contamination of firstsubstrate 26 or wafer 30 or both by particulate matter.

Specifically, the presence of particulate matter on substrate 26 maymanifest as many different shapes. For purposes of the presentdiscussion, one or more beads 36, shown in FIG. 2, having anasymmetrical area associated therewith may indicate the presences ofparticulate contaminants on either first substrate 26 or wafer 30.Further, with a priori knowledge of contaminants, specific shapes of oneore more beads 36 may be associated with a particular defect, such asparticulate contamination, as well as the presence of the defect, e.g.,on first substrate 26, wafer 30 and/or stage 14. This information may beincluded in a look-up table as discussed above so that processor mayclassify the defect and characterize first substrate 26 and/or wafer 30,accordingly.

Referring to FIGS. 1, 2 and 9, by analyzing information from two or morebeads, shown as 36 d and 36 e in region 22, the magnitude of thedistance “d” between first substrate 26 and wafer 30 may be concurrentlydetermined at differing sites. The distance information for each ofbeads 36 d and 36 e is determined as discussed above. Assuming beads 36d and 36 e have substantially identical areas, changes in the areas dueto first substrate 26 coming into mechanical contact therewith should besubstantially the same, were first substrate 26 and wafer 30substantially parallel and the distance, “d”, would be uniform overregion 22. Any difference between the areas of beads 36 d and 36 e aftermechanical contact with first substrate 26 may be attributable to firstsubstrate 26 and wafer 30 not being parallel, which could result in anon-uniform distance “d” between first substrate 26 and wafer 30 overregion 22. Further, the angle θ formed between first substrate 26 andwafer 30 may be determined from this information, as discussed above.Assuming that areas of beads 36 d and 36 e differed initially, similarinformation may be obtained by comparing the relative changes in theareas of beads 36 d and 36 e that result from mechanical contact withfirst substrate 26.

Specifically, it may be determined by analyzing the relative changesbetween areas of beads 36 d and 36 e it may be determined whether firstsubstrate 26 and wafer 30 at regions located proximate to beads 36 d and36 e are spaced apart an equal distance “d”. If this is the case, thenit may be concluded that first substrate 26 and wafer 30 extend parallelto one another. Otherwise, were first substrate 26 and wafer 30 foundnot to extend parallel to one another, the magnitude of the angle θformed therebetween may be determined.

Referring to FIGS. 1, 2 and 10, another advantage of examining multiplebeads in a regions, such as beads 36 f, 36 g, 36 h, 36 i and 36 j, isthat a shape of either first substrate 26 or wafer 30 may be obtained.This is shown by examining the changes in beads 36. For example, aftercompression of beads 36 f, 36 g, 36 h, 36 i and 36 j by first substrate26 each is provided with area 136 f, 136 g, 136 h, 136 i and 136 j,respectively that defines a compression pattern 137. As shown, beads 36f and 36 j have the greatest area, beads 36 g and 36 i have the secondgreatest area and bead 36 h has the smallest area. This may be anindication that first substrate 26 has a concave surface, i.e., isbowed, or that wafer 30 is bowed. From experimental analysis additionalinformation concerning differing types of compression patterns may beobtained to classify and characterize differing shapes or defects insystem 10. These may also be employed in look-up table 29 so thatprocessor 25 may match a compression pattern sensed by CCD sensor 23with a compression pattern in look-up table 29 and automaticallyascertain the nature of processing performed by system 10, i.e., whethersystem 10 is functioning properly and/or acceptable imprints are beinggenerated.

CCD sensor 23 may also be implemented for endpoint detection of thespreading of imprinting layer 34 over wafer 30. To that end, one or morepixel of CCD sensor 23 may be arranged to sense a portion of wafer 30.The portion, shown as 87 a, 87 b, 88 a and 88 b, in FIG. 7, is locatedin region 22 and is proximate to a periphery of imprinting layer 34after “d” has reached a desired magnitude. In this fashion, pixels ofCCD sensor 23 may be employed as an endpoint detection system thatindicates when a desired distance “d” has been achieved, therebyresulting in spreading of beads 36 to form imprinting layer 34 ofdesired thicknesses. This facilitates determining the magnitude ofmovement imprint head 12 should undertake in order to facilitate animprint of imprinting layer 34. To that end, once CCD sensor 23 detectsthe presence of imprinting layer 34 proximate to portions 87 a, 87 b, 88a and 88 b, data concerning the same is communicated to processor 25. Inresponse, processor 25 operates to halt movement of imprint head 12,fixing the distance “d” between first substrate 26 and wafer 30.

Referring to FIGS. 2, 7 and 11 in accordance with another embodiment ofthe present invention, detection system may include one or morephotodiodes, four of which are shown as 90 a, 90 b, 90 c and 90 d may beincluded to facilitate endpoint detection. Photodiodes 90 a, 90 b, 90 cand 90 d include wave shaping optics 91 and are arranged to sense apredetermined portion of first substrate 26, such as 88 a. However, itis advantageous to have photodiodes 90 a, 90 b, 90 c and 90 d senseportions 88 b, 87 a and 87 b, as well. For ease of discussion however,photodiodes 90 a, 90 b, 90 c and 90 d are discussed with respect toregion 88 a, with the understanding that the present discussion appliesequally to use of additional photodiodes to sense regions 87 a, 87 b and88 b.

To facilitate endpoint detections, photodiodes 90 a, 90 b, 90 c and 90 dare positioned to sense a portion of first substrate 26 that is locatedproximate to a periphery of imprinting layer 34 after “d” has reached adesired magnitude. As a result, photodiodes 90 a, 90 b, 90 c and 90 dmay be employed as an endpoint detection system as discussed above withrespect to CCD sensor 23 shown in FIG. 1. Referring again to FIGS. 2, 7and 11, photodiodes 90 a, 90 b, 90 c and 90 d are in data communicationwith processor 25 to transmit information concerning portions 88 a and88 b, such as intensity of light reflected from portions 88 a and 88 b.Specifically, portions 88 a and 88 b may be reflective, i.e., a mirrorreflects ambient onto photodiodes 90 a, 90 b, 90 c and 90 d. Upon beingcovered by imprinting layer 34, the energy of light reflecting fromportions 88 a and 88 b is substantially reduced, if not completelyattenuated, thereby reducing the power of optical energy impinging uponphotodiodes 90 a, 90 b, 90 c and 90 d. Photodiodes 90 a, 90 b, 90 c and90 d produce a signal in response thereto that is interpreted byprocessor 25. In response, processor 25 operates to halt movement ofimprint head 12, fixing the distance “d” between first substrate 26 andwafer 30. It should be understood that the detection system discussedwith respect to photodiodes 90 a, 90 b, 90 c and 90 d may be used inconjunction with CCD sensor 23 and wave shaping optics 24, discussedwith respect to FIG. 1. The advantage of employing photodiodes 90 a, 90b, 90 c and 90 d is that data acquisition is faster than that providedby pixels of CCD sensor 23.

Referring to FIGS. 2, 11 and 12, another embodiment of the presentinvention is shown that facilitates determining characteristics of firstsubstrate 26 and wafer 30 without knowing the volume associated withbeads 36. To that end, the present embodiment of system 110 includes aninterferometer 98 that may be used with the CCD sensor 23 thephotodiodes 90 a, 90 b, 90 c and 90 d or a combination of both. Asdiscussed above, system 110 includes wave shaping optics 24, radiationsource 16, mirror 20 and imprint head 12. Imprint head 12 retains firstsubstrate 26 disposed opposite wafer 30, with wafer 30 being supportedby stage 14. Processor 25 is in data communication with imprint head 12,stage 14, radiation source 16, CCD sensor 23 and interferometer 98. Alsodisposed in an optical path of interferometer 98 is a 50-50 mirror 120that enables a beam produced by interferometer 98 to be reflected ontoregion 22, while allowing CCD sensor 23 to sense region 22.

Use of interferometry facilitates determining distance “d” withouthaving accurate information concerning the initial volume of beads 36.An exemplary interferometry system employed to measure distance “d” isdescribed in U.S. patent application Ser. No. 10/210,894, entitled“Alignment Systems for Imprint Lithography”, which in incorporatedherein by reference.

Employing interferometer 98 facilitates concurrently determining theinitial distance “d” and the change in distance Δd. From thisinformation the volume associated with one or more beads 36 may beobtained. For example, interferometer 98 may be employed to obtain twomeasurements of first substrate 26 at two differing times t₁ and t₂ toobtain first substrate 26 displacement measurement L_(T). During thesame time, wafer 30 displacement measurement, L_(S), may be obtained, ina similar manner. The change in distance, Δd, between first substrate 26and wafer 30 is obtained as follows:Δd=|L _(T) −L _(S)|  (4)During times t₁ and t₂, measurements are taken with CCD sensor 23 todetermine the change in area of one or more of beads 36 as a function ofthe total number of pixels in which one or more of beads 36 are sensed.At time t₁, the total number of pixels in which one or more beads 36 aresensed is n_(p1). At time t₂, the total number of pixels in which one ormore beads 36 are sensed is n_(p2). From these two values the change inpixels, Δn_(p), is defined as follows:Δn _(p) =|n _(p2) −n _(p1)|  (5)From equations 4 and 5 the value of distance “d” may be obtained fromeither of the following equations:d ₁=(Δd/Δn _(p))n _(p1)  (6)d ₂=(Δd/Δn _(p))n _(p2)  (7)where d=d₁=d₂. Knowing d₁ and d₂, by substitution we can obtain thevolume V of the one or more beads 36 being sensed by CCD sensor 23 byeither of the following equations:V ₁ =d ₁(n _(p1)×pixelsize)  (8)V ₂ =d ₂(n_(p2)×pixelsize)  (9)where V=V₁=V₂, and (n_(p1)×pixelsize)=(n_(p2)×pixelsize)=A. When firstsubstrate 26 and wafer 30 may be maintained to be parallel,interferometer 98 may be measured outside of region 22, shown in FIG. 1.Otherwise, interferometer 98 measurements should be made proximate to acenter of region 22, or expanding beads 36. In this manner, thesubstrate 26 characteristic information obtained using system 10, shownin FIG. 1, may be obtained employing system 110, shown in FIG. 12.

The embodiments of the present invention described above are exemplary.Many changes and modifications may be made to the disclosure recitedabove, while remaining within the scope of the invention. Therefore, thescope of the invention should be determined not with reference to theabove description, but instead should be determined with reference tothe appended claims along with their full scope of equivalents.

1-20. (canceled)
 21. A system to determine system conditions bymeasuring characteristics of a volume of fluid disposed between a firstsubstrate, lying in a first plane, and a second substrate, lying in asecond plane, said system comprising: a displacement mechanism to causerelative movement between said volume and one of said first and secondsubstrates to effectuate a change in area of said first and secondsubstrates in superimposition with said volume; a detector system tosense said change in area and produce signals carrying informationconcerning said change in area; a memory containing a look-up table ofdata relating differing shapes of said volume to differing processingconditions; and a processing system, in data communication with saidmemory, to receive said signals and compare said information with saiddata and produce information corresponding to said system conditions.22. The system as recited in claim 21 wherein said processing conditionsinclude determining relative angular position between said first andsecond substrate.
 23. The system as recited in claim 21 wherein saidprocessing conditions including determining the relative parallelorientation of said first and second planes.
 24. The system as recitedin claim 21 wherein said processing conditions further includes thepresence of a defect in one of said first and second substrates.
 25. Thesystem as recited in claim 21 wherein said processing conditions furtherincludes the presence of a defect in one of said first and secondsubstrates and distinguishing between said first and second substratesas a source of said defect.
 26. The system as recited in claim 21wherein said processing conditions further includes the presence of aparticulate contaminant on one of said first and second substrates. 27.The system as recited in claim 21 wherein said processing conditionsfurther includes the presence of a particulate contaminant on one ofsaid first and second substrates and distinguishing between said firstand second substrates as a source of said particulate contaminant. 28.The system as recited in claim 21 wherein said processing conditionsfurther includes a distance between said first and second substrates.29. The system as recited in claim 21 wherein said processor determinessaid processing conditions in response to said change in areas measuredduring a period of time.
 30. A system to determine processing conditionsby measuring characteristics of a volume of imprinting material disposedbetween a first substrate, lying in a first plane, and a secondsubstrate, lying in a second plane, said system comprising: adisplacement mechanism to cause relative movement between said volumeand one of said first and second substrates to effectuate a change inarea of said first and second substrates in superimposition with saidvolume; a detector system to sense said change in area and producesignals carrying information concerning said change in area; a memorycontaining a look-up table of data relating differing shapes of saidvolume to differing processing conditions; and a processing system, indata communication with said memory, to receive said signals and comparesaid information with said data and determine one of said differingprocessing conditions associated therewith.
 31. The system as recited inclaim 30 wherein said processing conditions situations includedetermining relative angular position between said first and secondsubstrate.
 32. The system as recited in claim 30 wherein said processingconditions including determining the relative parallel orientation ofsaid first and second planes.
 33. The system as recited in claim 30wherein said processing conditions further includes the presence of aparticulate contaminant on one of said first and second substrates. 34.The system as recited in claim 30 wherein said processing conditionsfurther includes the presence of a particulate contaminant on one ofsaid first and second substrates and distinguishing between said firstand second substrates as a source of said particulate contaminant. 35.The system as recited in claim 30 wherein said processing conditionsfurther includes a distance between said first and second substrates.36. A system to determine processing conditions by measuringcharacteristics of a volume of imprinting material disposed between afirst substrate, lying in a first plane, and a second substrate, lyingin a second plane, said system comprising: a displacement mechanism tocause relative movement between said volume and one of said first andsecond substrates to effectuate a change in area of said first andsecond substrates in superimposition with said volume; a detector systemto sense said change in area and produce signals carrying informationconcerning said change in area; a memory containing a look-up table ofdata relating differing shapes of said volume to differing processingconditions; and a processing system, in data communication with saidmemory, to receive said signals and compare said information with saiddata and determine one of said differing processing conditionsassociated therewith.
 37. The system as recited in claim 36 wherein saidprocessing condition is one of a set of conditions selected from a setconsisting essentially of a relative angular position between said firstand second substrates, a relative parallel orientation of said first andsecond planes, the presence of a particulate contaminant on one of saidfirst and second substrates, and a distance between said first andsecond substrates.
 38. The system as recited in claim 36 wherein saidprocessing conditions further includes the presence of a defect in oneof said displacement mechanism, said first substrate and said secondsubstrate.
 39. The system as recited in claim 36 wherein said processingconditions further includes the presence of a defect in one of saiddisplacement mechanism, said first substrate and said second substrateand distinguishing between said displacement mechanism, said firstsubstrate and said second substrates as a source of said defect.